<!DOCTYPE html>
<html>
<body>
<form action="demo_form.asp">
Zip code: <input type="text" id="myText" name="zip_code">
<input type="submit">
</form>
<p>Click the "Try it" button to specify a regular expression that the text field's value will be checked against. Note that we also set the "title" to describe the pattern.</p>
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction() {
document.getElementById("myText").pattern = "[1-3]";
document.getElementById("myText").title = "A number from 1 to 3";
document.getElementById("demo").innerHTML = "The text field can now only contain numbers from 1 to 3.";
}
</script>
</body>
</html>